The long term goal of this proposal is to design, construct and clinically evaluate a real time volumetric (3D) ultrasonic imaging system which is also capable of visualizing and accurately representing blood flow in three dimensions. This instrument will permit the noninvasive assessment of tumor and organ volumes as well as cardiac chamber volumes. Such measurements have the potential of improving decision on tumor treatment, of assessing congenital and pathological states of various organs and of evaluating cardiac function on a serial basis. Incorporation of angle independent 3D flow measurements will permit the rapid noninvasive assessment of flow major peripheral vessels, deep abdominal vessels and coronary arteries. Flow imaging will also delineate the lumen of the vessel thereby simplifying detection of atherosclerotic plaques. The specific aims of the proposal include the upgrading of the Duke Phased Array Scanner to 256 transmit and receive channels and the development of improved 2D arrays. The proposed work is aimed at overcoming limitations in sensitivity and dynamic range which currently preclude clinical use. The upgraded system's performance will be assessed in terms of volumetric determinations in vitro and in vivo tests. The second major area of proposed work is directed towards the development of ultrasonic blood velocity measurement and imaging techniques which are suitable for visualizing flow in 3D. Two angle independent methods are to be studied. Based on in vitro and in vivo studies, one of these will be selected as most suitable for 3D flow imaging. Hardware will be constructed to implement this flow detection and measurement scheme. In vivo studies are proposed to validate the performance of the final system.